Results 1 to 1 of 1
Thread: Comparison of the Remington 6.8 SAAMI (SPC) and SPCII Chamber Comparisons Using the LMT 6.8 SPC 16"
-
13 March 2011, 15:38 #1
Comparison of the Remington 6.8 SAAMI (SPC) and SPCII Chamber Comparisons Using the LMT 6.8 SPC 16"
Please post comments here:
INTRO:
This is my Comparison of the Remington 6.8 SAAMI (SPC) and SPCII Chamber Comparisons Using the LMT 6.8 SPC 16" MRP Piston Upper.
TESTING:
The purpose of this test was to show the differences between the Remington 6.8 SPC SAAMI Chamber and the SPCII Chamber. I used the Nosler 115 GR BTHP, Hornady 110 GR BTHP, and the Hornady 110 GR V-MAX bullets for the testing. I used the LMT 6.8 SPC 16" MRP Piston Upper, which comes with the 1:10"/6-Groove/SAAMI Chamber for the testing. I tested the three bullets loaded to 2.245" with the SAAMI Chamber, then I converted the SAAMI Chamber to the SPCII Chamber using the SPCII Reamer and I tested the same three bullets loaded to 2.245". Then I tested the same three bullets in the SPCII Chamber, but this time loaded to 2.295". All loads were chrono'ed and I shot 3, 5 round shot groups for accuracy testing. Here are the results:
A: SAAMI CHAMBER:
Weapon: LMT 6.8 SPC 16" MRP Piston Upper (1:10"/6-Groove/SAAMI Chamber)
Optic: 4x16-44 Scope set on 16x.
Brass: SSA.
Crimp: Lee FCD.
OAL: 2.245".
Chrony Distance: (@10')
Temp: 43.
Nosler 115 GR BTHP:
Powder: 29 GR of AA2230.
Hi: 2372 fps, Lo: 2302 fps, Avg: 2348 fps, ES: 70, SD: 17
Accuracy (3 5 round shot groups):
Average: 2.146" (1.708", 1.994", 2.738").
Hornady 110 GR BTHP:
Powder: 29.5 GR of AA2230.
Hi: 2492 fps, Lo: 2411 fps, Avg: 2445 fps, ES: 81, SD: 25
Accuracy (3 5 round shot groups):
Average: 2.614" (2.393", 2.427", 3.023").
Hornady 110 GR V-MAX:
Powder: 29.5 GR of AA2230.
Hi: 2554 fps, Lo: 2455 fps, Avg: 2480 fps, ES: 99, SD: 27
Accuracy (3 5 round shot groups):
Average: 3.312" (3.069", 3.100", 3.768").
B: SPCII CHAMBER:
Weapon: LMT 6.8 SPC 16" MRP Piston Upper (1:10"/6-Groove/SPCII Chamber)
Optic: 4x16-44 Scope set on 16x.
Brass: SSA.
Crimp: Lee FCD.
OAL: 2.245".
Chrony Distance: (@10')
Temp: 43.
Nosler 115 GR BTHP:
Powder: 29 GR of AA2230.
Hi: 2372 fps, Lo: 2318 fps, Avg: 2344 fps, ES: 54, SD: 16
Accuracy (3 5 round shot groups):
Average: 2.199" (1.993", 2.106", 2.499").
Hornady 110 GR BTHP:
Powder: 29.5 GR of AA2230.
Hi: 2501 fps, Lo: 2411 fps, Avg: 2438 fps, ES: 90, SD: 22
Accuracy (3 5 round shot groups):
Average: 1.579" (1.191", 1.572", 1.976").
Hornady 110 GR V-MAX:
Powder: 29.5 GR of AA2230.
Hi: 2525 fps, Lo: 2428 fps, Avg: 2460 fps, ES: 97, SD: 25
Accuracy (3 5 round shot groups):
Average: 2.712" (2.534", 2.647", 2.957").
C: SPCII CHAMBER (MAX OAL):
Weapon: LMT 6.8 SPC 16" MRP Piston Upper (1:10"/6-Groove/SPCII Chamber)
Optic: 4x16-44 Scope set on 16x.
Brass: SSA.
Crimp: Lee FCD.
OAL: 2.295".
Chrony Distance: (@10')
Temp: 43.
Nosler 115 GR BTHP:
Powder: 29 GR of AA2230.
Hi: 2385 fps, Lo: 2306 fps, Avg: 2336 fps, ES: 79, SD: 18
Accuracy (3 5 round shot groups):
Average: 1.379" (1.000", 1.377", 1.761").
Hornady 110 GR BTHP:
Powder: 29.5 GR of AA2230.
Hi: 2482 fps, Lo: 2428 fps, Avg: 2452 fps, ES: 54, SD: 17
Accuracy (3 5 round shot groups):
Average: 1.781" (1.455", 1.866", 2.024").
Hornady 110 GR V-MAX:
Powder: 29.5 GR of AA2230.
Hi: 2515 fps, Lo: 2446 fps, Avg: 2481 fps, ES: 69, SD: 19
Accuracy (3 5 round shot groups):
Average: 1.998" (1.750", 1.824", 2.422").
VELOCITY COMPARISONS:
The velocity went down from the SAAMI to the SPCII Chamber from 4-21 FPS. I'm guessing this is from the reduced pressure. The thing that puzzles me is that the velocity went back up on 2 out of the 3 when I loaded the ammo long. I thought that loading the bullets long by .050", that it would reduce the pressure even more and the velocity would drop, which it did with the Nosler 115 GR BTHP, but with the Hornady bullets, the velocity went back up to where the SAAMI Chamber velocities were. Does this mean that the pressure went back up when I loaded the bullets long? It makes sense since the distance to the lands is the same with the bullets loaded to 2.245" in the SAAMI Chamber and when I loaded the bullets to 2.295" in the SPCII Chamber. This is where pressure testing would answer the question.
NOSLER 115 GR BTHP:
SAAMI CHAMBER: 2348 FPS
SPCII CHAMBER: 2344 FPS
Difference: -4 FPS
SPCII CHAMBER (MAX OAL): 2336 FPS
Difference: -8 FPS
HORNADY 110 GR BTHP:
SAAMI CHAMBER: 2445 FPS
SPCII CHAMBER: 2438 FPS
Difference: -7 FPS
SPCII CHAMBER (MAX OAL): 2452 FPS
Difference: +12 FPS
HORNADY 110 GR V-MAX:
SAAMI CHAMBER: 2480 FPS
SPCII CHAMBER: 2460 FPS
Difference: -20 FPS
SPCII CHAMBER (MAX OAL): 2481 FPS
Difference: +21 FPS
ACCURACY COMPARISONS:
In theory accuracy should be best with the SAAMI Chamber or when loaded to 2.295" in the SPCII Chamber. But it wasn't the case. With the Nosler 115 GR BTHP, the accuracy was the same with the SAAMI and SPCII Chambers and it improved by 0.820" when I loaded them to 2.295" in the SPCII Chamber. The Hornady 110 GR BTHP was the most accurate in the SPCII Chamber when loaded to 2.245", which is the farthest away from the lands. I don't actually mind this because this is the bullet I planned on using. The Hornady V-Max actually got better each time, which makes no sense at all, in theory.
Actually none of this comes as too much of a surprise to me. In the past, I have tested many bullets at different lengths and I got similar results. When I called Hornady and Sierra and spoke with the technicians, they both told me that every barrel is different. Some like the longer jumps, while other barrels like the shorter jumps. You can't take short cuts on this. When trying to find an accurate load, you have to play around with different powder charges and different OAL's. Don't just automatically load to 2.245" or 2.295" and give up on the bullet and powder if you don't get the desired results. The only problem is if you have the magazines that don't allow you to load long. Then you may just have to experiment with different powders.
NOSLER 115 GR BTHP:
SAAMI CHAMBER: 2.146"
SPCII CHAMBER: 2.199"
Difference: +0.053"
SPCII CHAMBER (MAX OAL): 1.379"
Difference: -0.820"
HORNADY 110 GR BTHP:
SAAMI CHAMBER: 2.614"
SPCII CHAMBER: 1.579"
Difference: -1.035"
SPCII CHAMBER (MAX OAL): 1.781"
Difference: +0.202"
HORNADY 110 GR V-MAX:
SAAMI CHAMBER: 3.312"
SPCII CHAMBER: 2.712"
Difference: -0.600"
SPCII CHAMBER (MAX OAL): 1.998"
Difference: -0.714"
CONCLUSION:
IMHO, there is no reason to have the SAAMI Chamber. The SPCII Chamber reduces the pressure by approximately 1500K PSI without the loss of accuracy.
PICTURES OF SHOT GROUPS:
SAAMI CHAMBER:
SPCII CHAMBER:
SPCII CHAMBER (MAX OAL):